Robotic end effectors are used to handle a variety of materials in the performance of repetitive tasks and to act as remote manipulators in hazardous or isolated environments. Although the tasks required of these mechanisms are diverse, to varying degrees they share common requirements for precision positioning, computerized control, resistance to jamming, and durability. Additionally, many tasks require a combination of compact size and high gripping forces. Finally, in specialized areas such as space construction, there are high premiums on high strength for weight and high penalties for mechanical failure.
Prior art has attempted to answer these competing demands, but sometimes with unacceptable compromises. For instance, when high gripping forces are obtained, the tendency of the mechanism to jam also rises. Additionally, high forces applied to complicated gear trains or transmission linkages promote wear and ultimately result in positioning errors.
Space applications require designers to coordinate exceptional demands for small size and light weight with those for power and high reliability. The goals for robotic manipulators include having the smallest motor possible coupled with a very strong and simple linkage which has a high mechanical advantage but will not jam under load. It is also desirable to have an end effector which, by the simple expedient of replacing a part or two, can be customized as to rate of motion and mechanical advantage without complete re-design of the mechanism.
Remote control of the gripping function requires the ability to determine the path necessary for the grippers to follow, as well as the ability to precisely position the grippers on the work piece. Both of these tasks, whether pre-programmed or performed interactively, are facilitated by true parallel gripper motion in a single axis of freedom. Many end effectors in present use have grippers which move both axially and radially when actuated. Parallel gripper motion minimizes both programming difficulties and operator errors.
Therefore, an object of the present invention is to provide an end effector mechanism which provides high gripping force through high mechanical advantage, while at the same time being resistant to jamming while under load.
A further object of the present invention is to provide an end effector with true parallel opposed jaw movement so as to provide advantages in programming and positioning over those prior art designs in which the jaws move both radially and axially upon actuation.
A further object of the present invention is to provide an end effector with as small a profile as possible so as to facilitate maneuvering in confined areas.
A further object of the present invention is to provide an end effector with a low probability of mechanical failure for applications such as radiological waste handling and space flight where failure costs are particularly high.
A further object of the present invention is to provide an end effector with a high ratio of grip strength to weight for applications such as space construction which place a premium on weight.
A further object of the present invention is to provide an end effector with highly accurate and repeatable gripper positioning by designing for optimally small clearances and very low operating friction.
A further object of the present invention is to provide an end effector with easily modifiable rate of motion and mechanical advantage characteristics so that it can be easily customized for specific applications.